(1) Field of the Invention
The present invention relates to a ceramic-metal composite body. More particularly, the invention relates to a ceramic-metal composite body in which an aluminum member and a ceramic member are integrally joined to each other through a ferrous metal member and an intermediate metallic member.
(2) Related Art Statement
Since aluminum has a small specific gravity as well as excellent ductility and corrosion resistance, it is used as structural materials and parts for aircrafts, vehicles, ships, industrial machines, etc. However, aluminum has a low melting point and is soft, so that it has poor heat and wear resistance.
To the contrary, ceramics have excellent heat and wear resistance. Thus, techniques have heretofore been investigated to join a ceramic member to a part of the aluminum member to form mechanical parts having light weight as well as excellent heat and wear resistance, such as pistons, rocker arms, etc. of internal combustion engines.
For example, Japanese Utility Model Registration application Laid-open No. 59-130,047 discloses a piston for an internal combustion engine in which an iron frame body with a threaded portion is shrinkage-fitted around the outer periphery of a ceramic sintered boy and the threaded portion of the frame body is screwed to a screw portion formed at a head portion of an aluminum alloy piston body.
In Japanese patent application Laid-open No. 56-122,659, there is disclosed a process for shrinkage-fitting a ferrous metallic member around the outer periphery of a ceramic top plate, and casting an aluminum alloy as a piston body around the metallic member.
Besides, Japanese Utility Model Registration application Laid-open No. 58-178,401 discloses a rocker arm for internal combustion engines, in which a ceramic tip is bonded to a rocker arm body with an organic adhesive.
Moreover, the piston disclosed in Japanese Utility Model application Laid-open No. 59-130,047 has a shortcoming wherein the connecting of the parts through screwing, causes an explosive pressure and a compression pressure to be lowered by an unnecessary space present at the threaded portion to reduce an engine efficiency. Further, since it is extremely difficult to always fix the positional relation between the ceramic member and the piston body through screwing, a special contrivance is necessary to constantly fix the positional relation beteen the ceramic member and the piston body.
On the other hand, the casting method disclosed in Japanese patent application Laid-open No. 56-122,659 has shortcomings that the structure of a mold becomes complicated, and careful attention is necessary lest the ceramic member should be broken during the casting or in a working step subsequent to the casting. Therefore, a specialized technique is required to enhance working automation.
Furthermore, the composite body using the organic adhesive as disclosed in Japanese Utility Model Resistration application Laid-open No. 58-178,401 has a shortcoming in that it can not be used in the case where a temperature at the joint rises.
As mentioned above, the composite bodies in which the ceramic member is joined to the aluminum member according to the heretofore proposed screwing, casting or bonding method have not been satisfactory.
To the contrary, a variety of other welding methods such as fusion welding, pressure welding, and brazing may be considered as methods appropriate for joining the ceramic member and the aluminum member. However, the ceramic member and the aluminum member cannot be fusion-welded or brazed together in ordinary manners.
Even if the ferrous metal member is fitted to the ceramic member as disclosed in Japanese Utility Model Resistration application Laid-open No. 59-130,047 and Japanese patent Laid-open No. 56-122,659, the ferrous metal member cannot be fusion-welded to the aluminum member. For, since the fusion welding is a method of joining two members by partially fusing both of them and where the temperature difference in melting point between the ferrous metal member and the aluminum member is too great, the aluminum member melts before the ferrous metal member melts.